Free radical initiated emulsion polymerizations are generally terminated by mixing the latices with a shortstopping agent that, under the prevailing conditions, almost immediately makes the initiator system inactive. There is available commercially a wide variety of shortstopping agents. The desirability of employing such agents is obvious in view of the need for obtaining rubbers possessing desired optimum characteristics. However, these shortstopping agents suffer from one or more shortcomings. For example, many of the commercially available compounds do not fall within what may be referred to as a "general purpose" category. For example, a shortstopping agent which might be entirely satisfactory for terminating "hot" butadiene-styrene systems (i.e., persulfate initiated polymerizations) may not be satisfactory in shortstopping "cold" butadiene-styrene systems where a powerful initiator (i.e., hydroperoxides) is used. On the other hand, shortstopping agents which may be used in both cold and hot rubber polymerization processes may possess or produce severe disadvantages such as imparting undesirable color to the rubber, being water insoluble, being susceptible to oxidation, or giving rise to materials which remain in the finished rubbers and cause undesirable and uncontrollable variations in vulcanization rates upon curing these rubbers. Another disadvantage might be the economic unattractiveness of the material as a commercial shortstopping agent brought about by the high costs of producing the material.
One particular problem arising from conventional shortstopping agents, such as the carbamate compounds and secondary amines, is that such compounds are easily nitrosated to form volatile nitrosamines. Volatile nitrosamines have recently become the subject of concern.